The present invention relates generally to a suspension control system for an automotive vehicle, which controls the damping force against the bouncing behavior of sprung body relative to unsprung wheels. More particularly, the invention relates to a control system for controlling a variable damping-force damper so as to reduce pitching motion of the vehicle body during deceleration of the vehicle.
Published Japanese Utility Model Application (Jikkai) Sho. 56-111009, discloses a suspension system having a variable shock absorber with adjustable shock-absorbing characteristics. The shock absorber is associated with a controller for controlling the damping force thereof. The controller operates the shock absorber to produce a higher damping force when it detects deceleration of the vehicle. The higher damping force is maintained as long as the vehicle brakes are applied to decelerate the vehicle. In other words, as soon as the brakes are released, the damping force to be produced by the shock absorber is reduced.
When applying brakes in order to stop the vehicle, the center of gravity shifts forward due to the inertia of the vehicle, which causes the vehicle to "nose dive". By adjusting the damping force to be produced by the shock absorber to HIGH, the magnitude of nose dive can be limitted. On the other hand, at the end of vehicle deceleration, the center of, gravity moves rearward, causing at the front end of the vehicle to rebound. In particular, when the brake is released immediately after stopping of the vehicle, the controller operates the shock aborber to lower the damping force. This may enhance the rebounding behavior of the vehicle and degrade riding comfort.
On the other hand, in the initial stage of deceleration of the vehicle, the pitching moment applied to the vehicle is quite high. The pitching moment gradually drops with the vehicle speed due to the reduction of counteracting torque on the axles. Therefore, a high damping force is required at the initial stage of braking or deceleration. After the vehicle stops, the center of gravity moves back to its initial position since the inertia has vanished, causing the vehicle body to rebound. To prevent this, a high damping force may be required. On the other hand, after the initial stage of vehicle deceleration, a low damping force would probably be adequate as substantial movement of the center of gravity does not occur during this stage.